The photoreceptor cell, though devoted to a singular function of absorbing a photon and creating an electrophysiological signal, accomplishes this process with a vast array of molecular machinery. We are interested in examining the less abundant accessory proteins present in the rod outer segment and wish to establish whether they play a direct role in triggering or regulation of the visual transduction process. We are isolating and characterizing photoreceptor cGMP phosphodiesterase and opsin kinase and will test these enzymes for functional roles in vitro reconstituted systems of artificial membranes containing the photoreceptor rhodopsin. Isolation of the mRNA coding for opsin, the protein component of rhodopsin. This material will be used to establish a bacteria clone containing recombinant DNA coding for the structural opsin gene. Such clones will provide us with information for the primary sequence of opsin as well as probes to investigate gene expression of rhodopsin in normal cells, neoplastic cells, and developing cells, opening new areas of study in vision.